Conventionally, as a heat exchanger for use in a vehicle such as an automobile, an aluminum laminate type heat exchanger having a core portion with flat tubes and fins disposed alternatively has been widely used. In such a heat exchanger, it is required to demonstrate heat exchanging performance even in the case of an occurrence of fin corrosion, and also required to have certain strength against chippings, etc. In general, after the occurrence of fin corrosion, the fin strength deteriorates due to intergranular corrosion.
In order to attain excellent material strength even in the case of an occurrence of fin corrosion, it has been known to use an aluminum alloy brazing sheet as a heat exchanger fin improved in intergranular corrosion resistance by regulating chemical composition of the core material and skin material. Also proposed is a method of preventing intergrannular corrosion of fins by regulating brazing conditions (see Japanese Unexamined Laid-open Patent Publication Nos. H11-140572 and 2003-326359).
However, the aforementioned methods of preventing intergranular corrosion could not sufficiently improve the self-corrosion resistance of fins, and therefore the fin strength could not be maintained under a severe condition exceeding a certain corrosion environment level.
In view of the aforementioned background technique, the present invention aims to provide a heat exchanger excellent in strength even in the case of an occurrence of corrosion, especially a heat exchanger having an excellent fin strength of a heat exchanger core front side requiring chipping proof performance. It also aims to provide a method of manufacturing the heat exchanger.